Process for making workpieces at least partly from metal powder



Unite Sta 7 2,932,883 PROCESS FOR MAKING WORKPIECES AT LEAST PARTLY FROMPOWDER V Richard Weber, Frankfurt am Main, Germany, assiguor toMetallgesellsc haft Aktiengesellschaft, Frankfurt am Main, Germany, acorporation offGerm'an'y No Drawing. Application August 5, 1955 SerialNo. 526,782

, .Claims prlority, app licatlon Germany August 5, 1954 4' Claims. (Cl.29420.5)

' flow of the metal treated to eifect their union. 7

The bodies formed in the first deformation operation may take the formof bars or sections. The second deformation operation may be effected,e.g., by extruding, drawing or forging. Bodies made by powder metallurgymay be bundled together with bodies made by other thanpowder-metallurgical operations, e.g. by casting or working (pressing,rolling, forging etc'.). The several bodies may agree or differ inproperties and/or composition.

Such a process has been disclosed in the co-pending U.S. PatentApplication Serial No. 339,175 filed February 26, 1953 now abandoned.

It has been found that the materials made in this manner, particularlywhen consisting of aluminum or aluminum alloys, show throughout theircross-section the boundaries between the several bundled bodies to aconsiderable degree. Whereas the several bodies formed in the firstdeformation operation are in fact united, the transitions can still berecognized. A closer inspection of these transition zones will show thatthey are enriched with largermetal particles and/or oxides, depending onthe composition of the material.

It is an object ofthe invention to improve the abovedescribed process ofmaking workpieces from metal powder, if desired in combination withnon-metallic powders such as alumina.

7 It is another object of the invention to provide a process of the typedescribed which will give workpieces of higher uniformity and transversestrength than comparable processes of the prior art.

According to the invention a surface layer is removed at least from theperiphery of the bodies formed by the first deformation operation. Thissurface layer consists of the skin formed on said bodies by said firstdeformation operation. The bodies are bundled only after said surfacelayer or skin has been removed. The removal may be effected, e.g., bypickling though the bodies formed by the first deformation operationcould also be machined on the lathe. The latter procedure, however,would involve an excessive loss of material and is more complicated.

In the case of aluminum and its alloys the pickling may be effected,e.g., with nitric acid and subsequent treatment in a 12% caustic sodasolution. This is preferably followed by a short dipping in hydrochloricacid and rinsing ofi the acid residues with water. The pickling of thebodies formed in the first deformation operation can also be eifected inaccordance with other known pickling processes to which the materialsubjected to the first deformation operation is responsive.

2,932,883 Patented Apr. 19, 1960 If the bodies formed in the firstdeformation operation are thus "pickled, the material deformed in thesecond deformation operation will no longer show distinct divisions atthe transitions between the several bodiesunited in the bundle nor willthese transitions be enriched with larger metal or oxide particles.

' The process according to the invention, in which the bodies formed bythe first deformation operation is subjected to a picklingtreatment toremove a surface layer from the-bodies before they are subjected to thesecond deformation operation results in workpieces of much more uniformstructureg. Such material can be worked and deformed in a higher degreeso that a higher-grade material is obtained.

"The pickling of the bodies to be bundled has only a small influence onthe strength properties in general though the transverse strength isincreased in a favorable manner by such pickling, particularly if thefirst deformation operation consists of extruding and the pickled bodiesare combined 'in a bundle in which they extend side 'by side in thedirection in which they were extruded. The cross-section of the materialmade from pickled bars and sections has a much improved appearancecompared to the material obtained when the bodies formed by the firstdeformation operation are bundled without such pickling or othertreatment to remove the surface layer. The process according to theinvention is particularly suitable for the manufacture of workpieceswhich are to be subjected to alternating stresses,'such as pistons. Theremoval of the skin resulting from the first deformation operation willimprove the deformability of the bundled material when being worked andthe structure of the resulting material.

The process may be explainedwith reference to an example:

A mixture of 28-30% silicon powder and 72-70% aluminum powder wascompacted and extruded to form bars 20 mm. in diameter. The deformationwas 1:12. The rods :were cut into sections having the length of thereceiver. Before the sections were bundled they were shortly dipped in5% nitric acid and then placed for 10 minutes in 12% caustic sodasolution. After removal fromthe caustic soda solution the bodies wereagain dipped for a short time in 5% nitric acid solution and thoroughlyrinsed with water. The rods thus pickled were bundled and extruded witha deformation of 1:12 to form a uniform bar 90 mm. in .diameter.

, material had been subdivided it was swaged to form pistons. Thepistons thus obtained are superior to those made without pickling. Thisis apparent already from the fact that the shaping. of the pistons isfacilitated and the pistons have a higher deformability (elongation) bythemselves.

Material made according to the invention is particularly suitable formaking parts to be stressed transversely to the direction in which itwas extruded because the transverse strength is higher than withoutpickling.

What is claimed is:

l. A process for making workpieces at least partly from aluminum powderand a powder of a substance to be alloyed thereto, which comprisesforming a plurality of bodies from a mixture of aluminum powder andpowder of said substance to be alloyed thereto by a first deformationoperation causing plastic flow of the aluminum, removing a surface layerat least from the periphery of said bodies, thereafter bundling saidbodies and subjecting said bundled bodies to a second deformationoperation which causes plastic flow of the aluminum treated to effecttheir union.

2.. A process for making workpieces at least partly from aluminumpowder, which comprises forming a plurality of bodies from powderconsisting at least partly After this of aluminum *by'a firstdeformation operation causing plastic flow of the aluminum, picklingsaid bodies to remove a surface layer therefrom, thereafter bundlingsaid bodies and subjecting said bundled bodies jointly to a seconddeformation operation which causes plastic flow of the aluminum treatedto efliect their union. 5 3. A process for making workpieces at leastpartly from aluminum powder, which comprises forming a plurality ofbodies at least partly from aluminum powder by a first deformationoperation causing plastic flow of the aluminum, removing a surface layerfrom said bodies by dipping them in pickling acid and placing themthereafter in a caustic alkali solution for a time relatively longerthan that for which they were dipped in said acid, thereafter bundlingsaid bodies and subjecting said bundled bodies jointly to a seconddeformation operation which causes plastic flow of the alu-1- minumtreated to effect their union.

' of aluminum'powder and 30-28 parts ofsilicon powder of the alumi'num,removing a surface layer from said 4. A process for making workpiecespartly from alubodies by dipping them in pickling acid and placing themthereafter in a caustic alkali solution for a time relatively longerthan thatfor'which they were dipped in said. acid, thereafter bundlingsaid bodies and sub: jecting said bundled bodies jointly to a seconddeformation operation which causes plastic flow o'f'the alloy treatedtoeffect their union.

' References Cited in the file of this patent 'UNITED STATES PATENTS2,024,767 Ieffries Dec. 17, 1935 2,252,697 Brassert Aug. 19, 19412,290,734 (Brassert July 21, 1942 2,332,737 Marvin Oct. 26, 19432,383,766 Brassert Aug. 28, 1945 2,404,808 7 Lowey July 30, 19462478,8561 Beaver Aug. 9, "1949 Lynch Jan. 23, 1951

1. A PROCESS FOR MAKING WORKPIECES AT LEAST PARTLY FROM ALUMINUM POWDERAND A POWDER OF A SUBSTANCE TO BE ALLOYED THERETO, WHICH COMPRISESFORMING A PLURALITY OF BODIES FROM A MIXTURE OF ALUMINUM POWDER ANDPOWDER OF SAID SUBSTANCE TO BE ALLOYED THERETO BY A FIRST DEFORMATIONOPERATION CAUSING PLASTIC FLOW OF THE ALUMINUM, REMOVING A SURFACE LAYERAT LEAST FROM THE PERIPHERY OF SAID BODIES, THEREAFTER BUNDLING SAIDBODIES AND SUBJECTING SAID BUNDLED BODIES TO A SECOND DEFORMATIONOPERATION WHICH CAUSES PLASTIC FLOW OF THE ALUMINUM TREATED TO EFFECTTHEIR UNION.